1. Field of the Invention
The present invention relates to an orbiting vane compressor, and, more particularly, to a low-pressure type orbiting vane compressor that is capable of diverging low-temperature and low-pressure refrigerant gas introduced into a shell through an inlet tube to an inlet port of a cylinder and a drive unit so as to simultaneously compress the refrigerant gas and cool the drive unit, and directly discharging compressed refrigerant gas out of a shell of the orbiting vane compressor.
2. Description of the Related Art
Generally, an orbiting vane compressor is constructed to compress refrigerant gas introduced into a cylinder through an orbiting movement of an orbiting vane in the cylinder having an inlet port. Various types of orbiting vane compressors, which are classified based on their shapes, have been proposed.
FIG. 1 is a longitudinal sectional view illustrating the overall structure of a conventional high-pressure type orbiting vane compressor. As shown in FIG. 1, a drive unit D and a compression unit P, which is disposed below the drive unit D, are mounted in a shell 1 while the drive unit D and the compression unit P are hermetically sealed. The drive unit D and the compression unit P are connected to each other via a vertical crankshaft 6, which has an eccentric part 6a. 
The drive unit D comprises: a stator 2 fixedly disposed in the shell 1; and a rotor 3 disposed in the stator 2 for rotating the crankshaft 6, which vertically extends through the rotor 3, when electric current is supplied to the rotor 3.
The compression unit P comprises an orbiting vane 4 for performing an orbiting movement in a cylinder 5 by the eccentric part 6a of the crankshaft 6. As the orbiting vane 4 performs the orbiting movement in the cylinder 5, refrigerant gas introduced into the cylinder 5 through an inlet port 51 is compressed. The cylinder 5 has an inner ring 52. Between the inner ring 52 and the inner wall of the cylinder 5 is defined an annular operation space 53. A wrap 40 of the orbiting vane 4 performs an orbiting movement in the operation space 53. As a result, compression chambers are formed at the inside and the outside of the wrap 40, respectively.
At the upper and lower parts of the compression unit P are disposed a main frame 7 and a subsidiary frame 7a, which support opposite ends of the crankshaft 6. The subsidiary frame 7a has a discharge chamber 8a, which is formed by a muffler 8. The discharge chamber 8a is connected to a pipe-shaped discharge channel 9, which extends vertically through the compression unit P and the main frame 7, such that the compressed refrigerant gas is discharged into the shell 1 through the discharge channel 9.
Unexplained reference numeral 11 indicates an inlet tube, 12 an outlet tube, and 10a an Oldham's ring for preventing rotation of the wrap 40 of the orbiting vane 4.
When electric current is supplied to the drive unit D, the rotor 3 of the drive unit D is rotated, and therefore, the crankshaft 6, which vertically extends through the rotor 3, is also rotated. As the crankshaft 6 is rotated, the orbiting vane 4 attached to the eccentric part 6a of the crankshaft 6 performs an orbiting movement.
As a result, the wrap 40 of the orbiting vane 4 performs an orbiting movement in the operation space 53 of the cylinder 5 to compress refrigerant gas introduced into the cylinder 5 through the inlet port 51 in the compression chambers formed at the inside and the outside of the wrap 40, respectively. The compressed refrigerant gas is discharged into the discharge chamber 8a through inner and outer outlet ports (not shown) formed at the cylinder 5 and the subsidiary frame 7a. The discharged high-pressure refrigerant gas is guided into the shell 1 through the discharge channel 9. Finally, the compressed refrigerant gas is discharged out of the shell 1 through the outlet tube 12.
FIG. 2 is a plan view, in section, illustrating the compressing operation of the conventional orbiting vane compressor shown in FIG. 1.
As shown in FIG. 2, the wrap 40 of the orbiting vane 4 of the compression unit P performs an orbiting movement in the operation space 53 of the cylinder 5, as indicated by arrows, to compress refrigerant gas introduced into the operation space 53 through the inlet port 51. The orbiting movement of the wrap 40 of the orbiting vane 4 will be described hereinafter in more detail.
At the initial orbiting position of the wrap 40 of the orbiting vane 4 of the compression unit P (i.e., the O-degree orbiting position shown in view (a) of FIG. 2), refrigerant gas is introduced into an inner suction chamber A1, which is disposed at the inside of the wrap 40, through the inlet port 51, and compression is performed in an outer compression chamber B2, which is disposed at the outside of the wrap 40, while the outer compression chamber B2 does not communicate with the inlet port 51 and an outer outlet port 53b. Refrigerant gas is compressed in an inner compression chamber A2, and at the same time, the compressed refrigerant gas is discharged out of the inner compression chamber A2.
At the 90-degree orbiting position of the wrap 40 of the orbiting vane 4 of the compression unit P (shown in view (b) of FIG. 2), the compression is still performed in the outer compression chamber B2, and almost all the compressed refrigerant gas is discharged out of the inner compression chamber A2 through an inner outlet port 53a. At this stage, an outer suction chamber B1 appears so that refrigerant gas is introduced into the outer suction chamber B1 through the inlet port 51.
At the 180-degree orbiting position of the wrap 40 of the orbiting vane 4 of the compression unit P (shown in view (c) of FIG. 2), the inner suction chamber A1 disappears. Specifically, the inner suction chamber A1 is changed into the inner compression chamber A2, and therefore, compression is performed in the inner compression chamber A2. At this stage, the outer compression chamber B2 communicates with the outer outlet port 53b. Consequently, the compressed refrigerant gas is discharged out of the outer compression chamber B2 through the outer outlet port 53b. 
At the 270-degree orbiting position of the wrap 40 of the orbiting vane 4 of the compression unit P (shown in view (d) of FIG. 2), almost all the compressed refrigerant gas is discharged out of the outer compression chamber B2 through the outer outlet port 53b, and the compression is still performed in the inner compression chamber A2. Also, compression is newly performed in the outer suction chamber B1. When the orbiting vane 4 of the compression unit P further performs the orbiting movement by 90 degrees, the outer suction chamber B1 disappears. Specifically, the outer suction chamber B1 is changed into the outer compression chamber B2, and therefore, the compression is continuously performed in the outer compression chamber B2. As a result, the wrap 40 of the orbiting vane 4 of the compression unit P is returned to the position where the orbiting movement of the orbiting vane 4 is initiated. In this way, a 360-degree-per-cycle orbiting movement of the wrap 40 of the orbiting vane 4 of the compression unit P is accomplished. The orbiting movement of the wrap 40 of the orbiting vane 4 of the compression unit P is performed in a continuous fashion.
Unexplained reference numeral 55 indicates a slider for maintaining the seal between the high-pressure and low-pressure parts.
In the conventional high-pressure type orbiting vane compressor according to the above-mentioned description, however, high-temperature and high-pressure compressed refrigerant gas is discharged into the shell. As a result, the temperature of the drive unit and the structural components of the orbiting vane compressor is excessively increased, and therefore, the drive unit and the structural components of the orbiting vane compressor are deformed or damaged. Consequently, the performance of the compressor is deteriorated, and the service life of the compressor is reduced.